(a) Field of the Invention
The present invention generally relates to a method and apparatus for a shared mesh protection switching.
(b) Description of the Related Art
Protection switching is a mechanism for rerouting traffic as soon as possible when the traffic is blocked by a failure in the network. The protection switching is classified as linear protection switching and ring protection switching according to network topology, and the linear protection switching is again classified as 1+1, 1:1, 1:N or M:N protection switching.
Basic protection switching scheme is 1+1 scheme. In the 1+1 scheme, there is a traffic path (hereinafter referred to as “protection path”) for protecting end-to-end traffic path (hereinafter referred to as “working path”).
According to the 1+1 scheme, under normal condition, a transmitting node simultaneously transmits traffic over the working path and the protection path, and a receiving node receives the traffic from the working path. When a failure occurs, the receiving node switches over to the protection path and receives the traffic from the protection path. The 1+1 scheme uses a simple protocol, but has a drawback of wasting half of network resources for the protection path.
The 1:1 scheme allocates one protection path for one working path, like the 1+1 scheme. However, in the 1:1 scheme, the traffic is transmitted over only the working path under normal condition, and the protection path is used when the failure occurs. Since the protection path can be used for transmitting less important traffic that does not need the protection switching under normal condition, the 1:1 scheme is more efficient than the 1+1 scheme.
The M:N scheme allocates M protections paths for protecting N working paths. In the M:N scheme, the network resources are used more efficiently than the 1:1 scheme. As M becomes smaller than N, the efficiency increases. However, in the M:N scheme, traffic can be protected only when a failure occurs in M or less working paths among the N working paths.
The 1:N scheme is a special case of M=1 in the M:N scheme, and operates in the same manner as the M:N scheme.
All of the protection switching schemes operates in one end-to-end linear protection domain. That is, two ends of traffic and working and protection paths for connecting the two ends are defined as one end-to-end linear protection domain, and a protection switching procedure is operated by exchanging messages between the two ends according to a protocol.
In the networks, various protection domains having different end nodes exist, but there is no mechanism that can coordinate the use of network resources between the end-to-end linear protection domains. As a result, the protection paths of end-to-end linear protection domains cannot share network resources.
Further, since priorities are not defined in the end-to-end linear protection domains according to the existing protection switching scheme, a specific end-to-end linear protection domain cannot be protected preferentially when limited network resources are shared.